USB booting :: Not bootable disk error message

I (think) I installed DSL as per directions to a 500Mb sub 2.0 pen drive. I have bios set to boot from USB HDD0: Flash Drive UR_USB20. When I try to boot directly from the pen drive I get the error message: This is not a bootable disk. I can however boot from the pen drive using the bootfloppy-usb disk. Can some one please tell me what to do to be able to boot from the pen drive without using the bootfloppy-usb disk?

Thanks

Mike

original here.